Environmental fluidic switching device with plural diaphragms

ABSTRACT

A fluidic switching device operating directly on ram air pressure differences to perform an electrical switching function. Operation is based upon the actuation of a micro switch by fluidic signal pressure acting against a flexible diaphragm and plate. The arrangement is self-compensating for altitude changes.

Umted States Patent 1191 1111 3,835,271 Garrett Sept. 10, 1974 [54] ENVIRONMENTAL FLUIDIC SWITCHING 3,006,363 10/1961 Jackson 251/118 UR q [me 3,571,542 3/1971 Madden 251/331 DEVICE WITH PL L DIAP GMS 3,770,012 11/1973 Bitzer 137/608 [75] Inventor: Abram J. Garrett, Canoga Park,

Calif.

[73] Assignee: The United States of America as 'f sch'flefer represented by the Secretary of the Asszstant Exammer-Gerald P. Tolm Navy, Washington, DC Attorney, Agent, or Firm-Richard S. Sciascia; l. M. St. Amand [22] Filed: Aug. 20, 1973 [21] Appl. No.2 389,859

ABSTRACT [52] US. Cl 200/83 Y, 200/83 SA, 137/610,

12 A fluidic switching device operating directly on ram I [51] Int. Cl. H0111 35/34 ai res ure differences to perform an electrical Fleld of Search 200/83 83 83 83 switching function. Operation is based upon the actua- 200/83 83 83 1316- tion of a micro switch by fluidic signal pressure acting 331 against a flexible diaphragm and plate. The arrangement is self-compensating for altitude changes. [56] References Cited UNITED STATES PATENTS 6 Claims 1 Drawing Figure 2,953,657 9/1960 Clements 200/83 Y CONTACT POINT DEVICE BOUNDRY PRESSURE CHAMBERS\\\\ 1 7 i FLEX RAM DIAPHRAGM AIR 1 ACTUATED INLET I BY dyn glLRlcJilc 7 7| UNES AIR fr SPEED /6 PRESSURE Y'l I FLEX AIR FILTER g c r u A i BY ENCLOSURE/'1// J ,8

STATIC AIR VENT PRESSURE SETTING RESTRICTORS (PNEUMATIC RESISTORS] ENVIRONMENTAL FLUIDIC SWITCHING DEVICE WITH PLURAL DIAPHRAGMS BACKGROUND OF THE INVENTION This invention relates to fluidic devices and more particularly to a ram air operated fluidic switching device. Prior fluidic operated switches are complicated devices involving moving valves or pistons, are not selfcompensating for environmental changes, have slow response, or do not function in a satisfactory manner.

SUMMARY oF THE INVENTION The present invention is a device which operates by ram air pressure generated by the speed of an aircraft carrying the device, for example, and responds directly to pressure signals of the airflow to actuate an electrical circuit at a predetermined airspeed. The air pressure is sensed by a dynamic pressure probe coupled to a differential pressure adjusted by a pneumatic resistance circuit.

A precision snap-acting microswitch is actuated by a differential pressure acting against a diaphragm and plate. It utilizes an extremely short stroke and a small volume permitting a fast response. The device is selfcompensating for altitude ambient air density variation. There is a normally off-function for no pressure, and there is a normally on-function for pressures greater than a specified magnitude, the value of which is predetermined by pneumatic resistors in the circuit.

BRIEF DESCRIPTION OF THE DRAWING The figure of drawing is a diagrammatic illustration of a preferred embodiment of the invention DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the figure of drawing, ram air enters the switching device via inlet 10. The device may be mounted on an aircraft or airborne vehicle. A filter 11 may be used to eliminate foreign matter from entering the device. The dynamic pressure of the ram air, caused by the aircraft speed, is sensed via passages 12 and 13 by both pneumatic flex-diaphragms 14 and 15 which contain the circuit contacts of the electrical circuit line 16. To close the switch at low aircraft speed, it is necessary to increase the restrictive value of pneumatic resistor R, relative to pneumatic resistor R To close the switch at high aircraft speeds, the value of R, is decreased relative to R Proper adjustment of pneumatic resistors R, and R regulate the air flow and pressure to the low pressure side of the diaphragms. Since pneumatic resistor R vents to the atmosphere via passage 18 and is influenced by that pressure, it is consequently affected by the altitude of the aircraft. The pneumatic pressure P to diaphragm 14 comes directly from the inlet pressure and its value is that of the dynamic air speed. The pneumatic pressure P,,,,,. on diaphragm is a resultant value of the pressures and air flow through resistors R, and R in the pneumatic circuit. The relation of the pressure of diaphragm 15 to that of diaphragm 14, necessary to make circuit contact, is as follows:

low dun (RZ/RI R2) To properly adjust this ratio of resistors, it is necessary to input to the device a dynamic air pressure corresponding to a prescribed aircraft speed. The resistors R, and R are then varied until an electrical close circuit is attained by diaphragms 14 and 15 contacting each other. Values of pneumatic resistors R, and R are selected to restrict the air passages. To obtain precision switching, at a predetermined aircraft speed, once set, these resistors remain fixed in the pneumatic circuit.

The diaphragms l4 and 15, which in effect form a precision snap-acting microswitch, are mounted within a chamber 19 which is housed in enclosure 20. Enclosure 20 also contains inlet passages 10, 12, 13 and 18. The operation is based on the actuation of the precision snap-acting micro switch by fluidic signal pressure acting against diaphragm l4 and diaphragm or plate 15. An extremely short stroke and small volume permits a fast response. As previously described, the device is self-compensating for altitude changes which affect the air density directly.

The fluidic switching device operates directly from pressure signals of the flowing fluid (air). As a result, no electrical power is required, making it ideal for use in environments where aircraft speed generates a pressure. This device provides a normally off-function with no pressure and normally on-function with pressures greater than specified magnitude whose value is predetermined by the pneumatic resistors R, and R in the circuit.

Pneumatic resistors R, and R may either be fixed for 0 a specific application or may be made adjustable so the device can be adjusted for different applications. As aforementioned, the switching device can be set to close at any select altitude and ram air pressure by adjusting R, and R When setting the switching device to close at a low ram air pressure at sea level, for example, the pressure P applied to diaphragm 14 will be low and the pressure P on diaphragm 15 must be increased by increasing the air flow through pneumatic resistor R, and lessening the flow through pneumatic resistor R If the device is-set to operate at a high altitude and at a high air speed, the pressure P on diaphragm 14 will be high and the pressure P,,,,, on diaphragm 15 must be lowered by increasing the flow through pneumatic resistors R, and R The amount of restriction needed to be provided by pneumatic resistors R, and R is determined by the required use of the device. The venting of the air pressure through the static air vent 18 by means of resistor R and the adjusting of resistors R, and R allows refinement of the opening and closing of the contact point of diaphragms 14 and 15 at a certain specified input pressure.

The test data given in Tables 1 through 4 show the performance of the device under normal sea level environment conditions.

The switching characteristics of the device were checked for repeatability and simulatedaircraft speeds required to trigger the switch. The data in Table 1 show 192 knots 223.68 mi/hr 328.32 ft/sec Required velocity ll ll ll -Continued Table 2 Air density 0.075 lb/ft (at sea level) Dynamic pressure. P4,", pV /2g US. Standard Atmosphere 2 (32.2) (144) Altltude* Temper Density Speed of Pressure 0.87 lb/in ature S und (Feet) (F) (lb/ft) (ft/s) (lh/ingl 59.00 0.0750 1.116 14.70 5.000 41.17 0.0646 1.097 12.23 The sensitivity of the switching limits can be in- 10900 2334 00554 L077 I d d d b l th d [0 15.000 5.51 0.0472 1.057 8.29 Credse l eSlrB VdI:ylng e ClI'C-Ll] lmpe 31108, 20 000 24 2 0 0 99 [036 75 R and R of the fluldic clrcuit shown 1n the figure of 2 .000 30.l5 0.0336 1.015 5.45 dnwin 30.000 47.99 0.0280 995 4.36 h v 35.000 65.82 0.0232 073 3.46 Atmospherlc dens1ty decreases w1th alt1tude. The re- 36.089 0 022 968 3.28 ir d ram air ressures used are shown in Tables 2 3 40000 69'70 OM84 968 6 P I i 1 45.000 69.70 0.0145 968 2.14 and 4. At an altltude of 40,000 feet, the device was 50.000 69.70 0.0114 968 1.68 found to stay energized as shown by the data in Table 55900 6970 00089 968 60.000 69.70 0.0070 968 1.04 In the sflnd 98 139 80 0 65.000 69.70 0.0055 968 0.82 65.800 69.70 0.0053 968 0.78 V6 f veloclty ft/S 70.000 67.30 0.0043 971 0.64 g Gravltauonal acceleration (32.2 ft/s 75,000 64.55 0.0033 974 0.51 paw Dynamic pressure lbfinza 80.000 -6l.8l 0.0026 977 0.40 p Air density of atmosphere, lb/ft P Ambient pressure, lb/in a Table 3 P Environmental chamber pressure, inches of c l ulations For Environmental mercury vac Fluidic Device 6 Aircraft Altitude Cruising Velocity 500 knots V 854.3 ft/s Altitude Dynamic Table 1 Pressure. P pVE/Zg Q X 854.3) 2 32.2 144 Switching ON/OFF Repeatabllity Tests 78699 p I I lnlet Prcssure of F luidi c Simulated Pr PM! Altitude Air Dcmhy p Flu1d1c Devlce (.ll'CUli Alrsgecd (lb/in!) (lb/m5) (Fuel) (lb/flu) Manometer Reading lh/in Open Closed l't/s Knots I; 590 1410 0 Q0750 will) 5.08 12.23 5.000 0.0646 4.36 10.11 10.000 0.0554 24.15 0.873 X 3 2- 3.71 8.29 15.000, 0.0472 23.80 0.864 X I 326.85 191.14 3.14 6.75 20.000 0.0399 24.40 0.882 X 329.68 192.79 2.64 5.45 25.000 0.0336 23.90 0.864 X 326.85 191.14 2.20 4.36 30.000 0.0280 24.40 0.882 X 329.68 192.79 40 1.83 3.46 35.000 0.0232 23.90 0.865 X 326.45 190.90 3 8.833 8.82%: 24.45 0.884 X 330.61 193.34 4 A 23.95 0.866 x 326.64 191.02 114 45900 00145 24.40 0.882 x 329.68 192.79 508000 00114 0.70 1.32 55.000 0.0089 0.55 1.04 60.000 0.0070 0.43 0.82 65.000 0.0055 Switching values: 0.34 0.78 70.000 0.0043 Average Speed 192.00 knots 026 064 75000 00033 Average fluidie pressure .87 lb/in 020 040 0 000 00026 Table 4 Flight Parameters for Environmental Fluidic Device Simulated Speed Ram Pressure P Altitude PM, Fluidic (Feet) Inches of (lblin a) Inches of Circuit Knots ft/s lblin a lb/in Mercury Mercury Sea-Level 0 0.0 0.0 0.00 0.00 14.70 0 0 Open 0 50.0 85.5 0.06 0.12 14.70 0 0 Open 0 100.0 171.0 0.24 0.49 14.70 0 0 Open 0 190.7 326.09 0.86 1.75 14.70 0 0 Closed Cruising 0 500 855 5.90 12.01 14.70 0.00 0.00 Closed 5.000 5.08 10.34 12.23 2.47 5.03 10.000 4.36 8.87 11.11 3.59 7.31 15,000 3.71 7.55 8.29 6.41 13.05 20.000 3.14 6.39 6.75 7.95 16.18 25,000 2.64 5.37 5.45 9.25 18.83 30,000 500 855 2.20 4.48 4.36 10.34 21.04 Closed Table 4-Coi 1tinued Flight Parameters for Environmental Fluidic Device Simulated Speed Ram Pressure P Altitude P Fluidic (Feet) inches of (lb/ina) Inches of Circuit Knots ft/s lblin a lb/in Mercury Mercury i tkfint uss 35,000 500 855 1.83 3.72 3.46 11.24 22.88 Closed 36,089 1.75 3.56 3.28 11.42 23.24

50,000 0.89 1.81 1.68 13.02 2650 Closed 55,000 0.70 1.42 1.32 13.38 27.23 Open 60,000 0.55 1.12 1.04 13.66 27.80

practiced otherwise than as specifically described.

The environmental fluidic switching device described herein can be used for environmental safing and fuzing of ordnance systems.

Some of the attractive features of this fluidic switching system are: high reliability, operation under extreme environmental conditions, resistance to radia-- tion, and low cost. This fluid system is inherently very reliable by virtue of the fact that the only moving parts are the diaphragms. No electrical power is required, making the fluidic device ideal for use inenvironments where aircraft speed generates a pressure.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be 1 claim:

l. A fluidic switching device operable in response to dynamic and environmental air pressure differences, comprising:

a. a housing;

b. a pressure chamber within said housing;

0. pressure sensing means mounted within said pressure chamber;

d. said pressure chamber being divided into two separate compartments by said pressure sensing means; each of said two pressure chamber compartments, 7 respectively, having only a single fluid flow part thereto;

e. a ram air inlet to said housing;

f. a first passageway in said housing from said ram air inlet directly to the fluid flow port of the first of said two pressure chamber compartments, where dynamic ram air pressure is sensed;

g. a second passageway in said housing from said ram air inlet to the fluid flow port of the second of said two pressure chamber compartments;

h. a third passageway in said housing from the fluid flow port of the second of said two pressure chamber compartments to the ambient atmosphere;

1. a separately adjustable pressure setting restrictor in each of said second and third passageways, respectively, said second and third passageways and restrictors forming a pneumatic resistance circuit, the pressure in the second of said two separate compartments being adjusted to provide a differential in pressure between the two compartments when there is ram air pressure at the ram air inlet; said device being selfcompensating for altitude am- Open bient air density variation;

j. said pressure sensing means sensing the pressure differential between said two compartments and operable to actuate an electrical circuit connected thereto at a selected desired differential in pressures;

k. said pressure sensing means comprising first and second spaced apart, flexible diaphragms actuated by the differential in pressure in said two compartments, the spaced apart diaphragms containing electrical contacts to said electrical circuit and forming a pressure actuated switch means;

1. said first and second flexible diaphragms being normally separated at no pressure differential wherein the switch is thus normally open at no pressure differential, and said first and second diaphragms making electrical contact and thus closing the switch for pressures greater than a specified magnitude, the pressures required to close the switch being predetermined by the setting of said pressure setting restrictors;

m. the pressure in each of said pressure chamber compartments being sensed by said first and second pressure sensing diaphragms, the ram air pressure being sensed in the first of said pressure chamber compartments directly on said first diaphragm via said first passageway and partially in said second compartment on said second diaphragm via said second passageway, said second compartment being the low pressure side of said pressure chamber, and the pneumatic pressure on said second diaphragm being a resultant value of the pressures and air flow through the pressure setting restrictors in said second and third passageways, a closed electrical circuit being attained when the pneumatic pressures on said first and second diaphragms cause the two diaphragms to contact each other, the device actuating at low altitude and low ram air pressures when the restrictive value of the restrictor in said second passageway is increased relative to the value of the restrictor in said third passageway, and the device being actuated at high altitude and high ram air pressures when the restrictive value of the restrictor in said second passageway is decreased relative to the value of the restrictor in said third passageway. 2. a device as in claim 1 wherein said pair of spaced apart diaphragms form a precision snap-acting microswitch.

3. A device as in claim 2 wherein said snap-acting mi croswitch utilizes a short stroke and small volume permitting fast response.

4. A device as in claim 1 wherein a filter means is provided at the entrance to said ram air inlet to eliminate any dirt and foreign matter which would operate to clog the passageways from entering therein.

5. A device as in claim 1 wherein the ram air pressure is provided and generated by the speed of an aircraft carrying said device.

6. A device as in claim 1 wherein the relationship of pressures necessary to actuate the device is expressed by the following formula:

low dun Z I i 2] 

1. A fluidic switching device operable in response to dynamic and environmental air pressure differences, comprising: a. a housing; b. a pressure chamber within said housing; c. pressure sensing means mounted within said pressure chamber; d. said pressure chamber being divided into two separate compartments by said pressure sensing means; each of said two pressure chamber compartments, respectively, having only a single fluid flow part thereto; e. a ram air inlet to said housing; f. a first passageway in said housing from said ram air inlet directly to the fluid flow port of the first of said two pressure chamber compartments, where dynamic ram air pressure is sensed; g. a second passageway in said housing from said ram air inlet to the fluid flow port of the second of said two pressure chamber compartments; h. a third passageway in said housing from the fluid flow port of the second of said two pressure chamber compartments to the ambient atmosphere; i. a separately adjustable pressure setting restrictor in each of said second and third passageways, respectively, said second and third passageways and restrictors forming a pneumatic resistance circuit, the pressure in the second of said two separate compartments being adjusted to provide a differential in pressure between the two compartments when there is ram air pressure at the ram air inlet; said device being selfcompensating for altitude ambient air density variation; j. said pressure sensing means sensing the presSure differential between said two compartments and operable to actuate an electrical circuit connected thereto at a selected desired differential in pressures; k. said pressure sensing means comprising first and second spaced apart, flexible diaphragms actuated by the differential in pressure in said two compartments, the spaced apart diaphragms containing electrical contacts to said electrical circuit and forming a pressure actuated switch means; l. said first and second flexible diaphragms being normally separated at no pressure differential wherein the switch is thus normally open at no pressure differential, and said first and second diaphragms making electrical contact and thus closing the switch for pressures greater than a specified magnitude, the pressures required to close the switch being predetermined by the setting of said pressure setting restrictors; m. the pressure in each of said pressure chamber compartments being sensed by said first and second pressure sensing diaphragms, the ram air pressure being sensed in the first of said pressure chamber compartments directly on said first diaphragm via said first passageway and partially in said second compartment on said second diaphragm via said second passageway, said second compartment being the low pressure side of said pressure chamber, and the pneumatic pressure on said second diaphragm being a resultant value of the pressures and air flow through the pressure setting restrictors in said second and third passageways, a closed electrical circuit being attained when the pneumatic pressures on said first and second diaphragms cause the two diaphragms to contact each other, the device actuating at low altitude and low ram air pressures when the restrictive value of the restrictor in said second passageway is increased relative to the value of the restrictor in said third passageway, and the device being actuated at high altitude and high ram air pressures when the restrictive value of the restrictor in said second passageway is decreased relative to the value of the restrictor in said third passageway.
 2. a device as in claim 1 wherein said pair of spaced apart diaphragms form a precision snap-acting microswitch.
 3. A device as in claim 2 wherein said snap-acting microswitch utilizes a short stroke and small volume permitting fast response.
 4. A device as in claim 1 wherein a filter means is provided at the entrance to said ram air inlet to eliminate any dirt and foreign matter which would operate to clog the passageways from entering therein.
 5. A device as in claim 1 wherein the ram air pressure is provided and generated by the speed of an aircraft carrying said device.
 6. A device as in claim 1 wherein the relationship of pressures necessary to actuate the device is expressed by the following formula: Plow Pdyn (R2/R1 + or - R2) where: Plow pressure in said second compartment Pdyn pressure in said first compartment R1 restrictive value of the restrictor in said second passageway R2 restrictive value of the restrictor in said third passageway. 